troubleshooting My PC giving me "RAM" error

[Vk_vule]

Hi

After a while of gathering used stuff (some new) I managed to complete my PC build.

As I went to turn it on, I see red light indicating that something isn't right with RAM.

PC isn't starting at all, just plain red light if RAM is in DDR4_1_ slot
If there isn't RAM stick in first slot, CPU and RAM icons are randomly blinking and ventilator on PC is turning ON/OFF, after 10 seconds it restarts and do it again.

My specs are:

Gigabyte GA-H270-HD3 (Used)

Corsair Vengeance LPX DDR4 2666MHz c16 cmk16gx4m4a2666c16r - (usualy comes in 4x4gb pack; but I bought 2x4gb (used)

Intel Pentium g4560 (New)

MSI GeForce GTX 970 (Used)

Antec NeoEco Classic NE550C (New)

 

Can this be caused by ram being at 2666MHz, while MBO/CPU support 2400MHz. I tried using just one stick of ram, every slot, different combinations.

I tried restarting BIOS, (don't know if it worked or not, since I can't access it)

Yes, I checked if I placed RAM correctly.

 

Any help would be appreciated. Thanks in advance!